Question

To construct a calibration curve we would need to take our stock solution and dilute it to different concentrations. We would then test those different concentration in our spectrophotometer to test their absorbance. If we diluted our samples as follows, calculate the resulting concentrations. (HINT: this is dilution which means we can use M1V1=M2V2, where M1 is our original 150 mM concentration, V1 is the volume of the original concentration that we added water to dilute, M2 is the concentration we want to solve for, and V2 is the total volume (stock solution + water). The original volume was 100.00 mL.

Table 2: Dilution of Co(NO3)2

Sample Number	mL Co(NO3)2	mL DI water	Concentration (mM)
0	0.00	5.00
1	1.00	4.00
2	2.00	3.00
3	3.00	2.00
4	4.00	1.00
5	5.00	0.00

Answer 1

Stock solution concentration = 150 mM

Let M1 and V1 be the molarity and volume of (CoNO3)2

M2 and V2 be the molarity and volume(stock solution + water) of the final solution

Sample number 0

M1V1 = M2V2

0.150 M x 0 = M2 x 5 mL

M2 = 0 M

M2 = 0 mM

Sample number 1

M1V1 = M2V2

0.150 M x 1 = M2 x 5 mL

M2 = 0.03 M

M2 = 30 mM

Sample number 2

M1V1 = M2V2

0.150 M x 2 = M2 x 5 mL

M2 = 0.06 M

M2 = 60 mM

Sample number 3

M1V1 = M2V2

0.150 M x 3 = M2 x 5 mL

M2 = 0.09 M

M2 = 90 mM

Sample number 4

M1V1 = M2V2

0.150 M x 4 = M2 x 5 mL

M2 = 0.12 M

M2 = 120 mM

Sample number 5

M1V1 = M2V2

0.150 M x 5 = M2 x 5 mL

M2 = 0.150 M

M2 = 150 mM

Sample number	mL of Co(NO3)2	mL of DI water	Concentration (mM)
0	0.00	5.00	0
1	1.00	4.00	30
2	2.00	3.00	60
3	3.00	2.00	90
4	4.00	1.00	120
5	5.00	0	150